A pharmaceutical injection device typically comprises a main body case having an injection needle mounting portion at a first end, a pharmaceutical syringe mounting portion provided inside the main body case, a piston provided movably with respect to a pharmaceutical syringe mounted to the pharmaceutical syringe mounting portion, and a drive mechanism for driving the piston.
That is, with a conventional pharmaceutical injection device, first the pharmaceutical syringe is mounted to the pharmaceutical syringe mounting portion, and then the injection needle is mounted to the injection needle mounting portion. After this, the injection needle pierces the skin of the patient, and then a packing inside the pharmaceutical syringe is pushed by the piston through force from the drive mechanism, which injects the pharmaceutical inside the pharmaceutical syringe through the injection needle and into the patient's body.
Sometimes a cover that covers the injection needle mounting portion is removably mounted to the main body case in order to prevent the injection needle mounting portion from becoming dirty.